Printing telegraph apparatus



L. DEVAUX 2,226,698

PRINTING TELEGRAPH APPARATUS Filed June 26, '19s"! ATTORNEY PatentedDec. 31, 1940 PATENT OFFICE PRINTING TELEGRAPH APPARATUS Lucien Devaux,Paris, France, assignor to International Standard Electric Corporation,New

York, N. Y.

Application June 26, 1937, Serial No. 150,466 In France June 29, 1936 6Claims.

In a large number of telegraph receivers known at the present time,particularly in receivers which reproduce lettersand signs by dots closetogether, it is necessary to obtain a very rapid movement of the .memberproducing the impression. For this purpose electro-magnetic systems areemployed whose movable portion is very light and which receive ratherintense current in order to obtain a rapid movement of the I armature.

The present invention provides the control of the printing member by adevice employing the properties of piezo-electrlc crystals. vIt is knownthat by cutting laminations after having provided them witharmatures,bi-la'minal or multi-laminal units are obtained, which bend whendifferences of potential are applied between the armatures, thedirection of distortion depending on the difference of potential.Rochelle salt (a double tartrate of potassium and sodium) isparticularly suitable for this application because, for the samedifference of potential it undergoes far greater distortions than othercrystals which have been tested.

Such a device may be adapted to actuate either a printing stylus, whichpresses carbon paper on the registering tape or a knife which lifts thepaper tape to apply it to a carbon paper or the like Whose other side isresting on a moving point, either a small plate which controls movingstyluses, or any other member acting in a similar manner. Any suchmember may be called a printing hammer. The advantage of this system isthat it is easy to obtain a rapid movement following with precision therhythm of the transmission, and the device does not require permanentcurrent; it is suilicient to maintain the difference of potentialwithout output, in order to maintain the pressure.

The amplitude of the movement of a piezoelectric crystal is generallytoo low for it to be possible to control the printing member directly,but the pressures obtained being great it is possible to amplify themovement by mechanical means, such as a lever or by other arrangementssuch as pneumatic devices.

An embodiment of the invention is shown by way of example in theaccompanying drawing, in which Fig. 1 illustrates schematically anarrangement in accordance with the invention, and

Fig. 2 illustrates a form of control circuit in accordance with theinvention.

Fig. 1 of the accompanying drawing shows schematically the embodiment ofa printing arrangement in a telegraph receiver. The piezoelectricreceiving unit I is formed of several superposed strips; it is square inshape and supported at three of its corners by means of elastic plates,2, such as rubber. The plates are cut in such a way that in applying adifference of potential between the armatures 3 and 4 the strips bend insuch a way that the free corner 5 is displaced along a lineperpendicular to the plane of the strips. This corner is assembled witha small rod 6 which actuates a lever I pivoting round an axis 8. Theother end of the lever is provided with the member serving for printing.

In the case of the drawing, a small hammer 9 strikes on the styluses I0,ll, l2, l3, l4, l5, I6 carried by a carriage I1, and serves to press aninked ribbon I8 on a paper band l9. The carriage I! is moved by analternative movement which is synchronised with the transmission in sucha way that the styluses Ill-l6 pass through parallel lines, andaccording to the action of the hammer 9 trace dots or dashes whosearrangement forms theletters. For example the carriage I1 may bereciprocated by means of a cam on a shaft released for one rotation atthe commencement of receipt of impulses representing a character.

The movement of the lever may be doubled without increasing theconstraint of the crystal. For this purpose the receiving circuit may bearranged so that in the normal condition the crystal is polarised in onedirection and that the reception of the signals produces a polarisationof opposite sign and of the same value. An example of such a circuit isgiven in Fig. 2 of the accompanying drawing.

The piezo-electric crystal 20 is connected in the diagonal of aWheatstone bridge two branches of which are formed by two equalresistances 22 and 23, and the two other branches of which are formed bytwo electron tubes 24 and 25. The grid of tube 24 is normally stronglypolarised so that the resistance of the tube is considerable, and on theother hand the grid of tube 25 is neutral and the resistance of the tube25 is low.

The crystal is thus polarised in one direction.

Included in the grid circuits of tubes 24 and 25 are diodes 26 and 21respectively, and these circuits are connected to the last tuned circuit28 of the receiving station in such a way that a received impulse makesthe grid of tube 24 become negative.

The bridge is thus unbalanced in the inverse direction and thepolarisation of the piezo-electric elements is reversed.

It is clear that the invention is not limited to the embodiment whichhas just been described, but that on the contrary it is capable ofgeneral applications. It is thus that instead of a single pieZo-electricelement it is possible to use one such element in each of severalchannels each controlling a separate printing hammer, in the case inwhich impulses representing a character are sent over several channels.

What is claimed is:

1. A printing telegraph receiver adapted to record signals by marksrepresenting the various characters in accordance with received signalimpulses, comprising a plate built up of a plurality of laminations eachcut from a crystal piezo-electric material, means for applying receivedsignal impulses to opposite sides of said plate to cause said plate todeform, and a printing hammer cooperating with said plate actuatable inresponse to the deformation of said plate for recording said receivedsignals.

2. A printing telegraph receiver adapted to record signals by marksrepresenting the various characters in accordance with received signalimpulses, comprising a plate of piezo electric material, means forapplying received signal impulses to opposite sides of said plate tocause said plate to deform, a printing hammer cooperating with saidplate actuatable in response to the deformation of said plate forrecording said received signals, a carriage mounted for cooperation withsaid printing hammer, and a plurality of 3 styluses mounted in saidcarriage for selective positioning with respect to said hammer, wherebyoperation of said printing hammer in accordance with received signalimpulses serves to build up representation of said characters throughoperation of said styluses.

3. A printing telegraph receiver in accordance with claim 1, in whichthe means for actuating said printing hammer comprises a lever, one endof said lever being in contact with a corner of said piezo-electricplate, and the other end of said lever carrying said printing hammer.

4. A printing telegraph receiver in accordance with claim 1, furthercomprising means for normally polarizing said plate in one direction, inwhich said received impulses produce polarization of said plate'in theopposite direction.

5. A printing telegraph receiver comprising a Wheatstone bridgearrangement, thermionic tubes in adjacent arms of said Wheatstone bridgearrangement, resistance elements in the other arms of said bridge, meansfor normally biasing said thermionic tubes so that one of said tubespresents a low resistance and the other of said tubes represents a highresistance, a plate of piezoelectric material bridged across onediagonal of said Wheatstone bridge circuit, a telegraph signal recordingmeans cooperating with said plate, and a receiving circuit connectedwith said thermionic tubes for reversing the biasing effect on saidtubes in response to received signal impulses.

6. A printing telegraph receiver according to claim 1 for comprisingelastic members for supporting said built-up plate at three of itscorners whereby a fourth corner is capable of vibrating along a linesubstantially perpendicular to the plane of the plates, and a leverhaving one end in engagement with said fourth corner and the other endprovided with said printing hammer.

LUCIEN DEVAUX.

